I'm not getting the warm and fuzzies from the damper mounts though. Are you going to brace those towers to each other and/or down to the new frame rails?

I've thought a lot about this over the years. The solution that I've seen on cars like the F40 and the RS200 is to just join the two towers. So, I've worked out a solution.

The design was not really inspired by either of these cars, but they both sport IRS's with high mount coil overs that are similar to what I'm working with. It's a little "old school" compared with how it would be done today and I could have switched it up to have either cantilevered or offset coil overs, but packaging was harder.

Here's what I've done. I made an exact scale replica of the rear shock towers using 3/32" TIG rod. Then I analysed the various stresses as I added parts. Sorry I didn't take pictures of the entire thing, you get the idea.

Without any cross bracing at all, the "towers" were very easy to move in bump or droop. They could be bent in every direction. Then with the addition of just the cross brace, all that happened was motions on one side were transmitted to the other side. it was a little stiffer, but I don't think I could characterise it as better, in fact worse in some ways as the motions were translate which would add to the stresses over time.

Then I added some 1/16" TIG diagonal braces following what was shown in the F40 and RS200. I used 1/16" as they used smaller tube and I happen to have some 1" 100 wall DOM. Bam - I can not make this move laterally at all. Or at least not with just simple hand movements. If I went full gorilla on it - sure, but the only thing you can do with this shape is twist it a bit which is not a force that it would see unless something catastrophic went wrong. It was shocking how much of a difference this made.

The entire design is actually done - so I'll just bomb away with what I did.

You can see it a little better this way.

This gives me easy access to the shock bolt and other potential service items and I don't think sacrifices strength where needed. It also does meet my objective of getting the bar up and out of the way a little so the space isn't gratuitous in the trunk.

Bar in place.

Then I added the diagonals.

Both the tops and bottoms of this bar are attached using 1/2" captive nuts as I don't want to be working with more than one socket to take it out if the need should ever arise.

There are 1/8" plate doublers on the frame rails with nuts welded on to the plates. It's not all tacked up as I'm out of argon and that will have to wait for another day.

The main bar went together with 1/2" button welds plus the closing plates. It's not going anywhere.

Once welded - it's not going anywhere.

The idea is that it can come out to make removal a little easier...but in the end it didn't matter when I refit the subframe. So it is what it is.

I'll post the rest later - It needs some serious sorting so this thread continues to "make sense" from a build perspective.

Time for another update. I have to try to remember where this all left off (takes a moment to scroll down - right)...it's been too long.

So the front brackets for the subframe are all welded in and I made sheet metal returns up to the floor pan. Start with some 20 ga bent to 90 degrees and stretch to make the curve.

That gets these done faster than you think.

Then weld them on and tidy up the welds.

Then I thought that even with the gussets, it might be worth boxing the top of the seat pan and joining it to the cross member for extra unneeded strength. So I made some cardboard templates (I'm getting good at these now).

Scribed them onto some 18 ga steel (love the smell of blueing).

And got to work bending this all up.

Good patterns produce good parts.

Welded up the joins.

Welded them in place - the tricky part was accounting for the slope of the cross member.

Seat fits in and you can't see a thing - perfect.

Then I gave the subframe a quick shot of black paint to hold it until I'm done fabricating and get it powder coated.

Stuffed it all back in the hole and started to work out the sheet metal for the trunk.

Turns out I didn't need to make the strut bar removable, but it was probably easier to fabricate this way - or at least that's what I'm telling myself.

Time for some serious pattern making.

I also made this panel - didn't take pictures of how. It's just a closing panel with dimples and flanges.

This is hands down the best best thread on TB. Constant source of inspiration, even though anything I'm doing is at about 2% of your project's level.

Also, what are you going to put in that BBQ trunk space? Fuel cell?

Thanks for the kind words. The BBQ lid is really sort of a concession to my dislike for the current hot rod trend of sheet metal that just blocks everything out when you've modded things. Sure it's easy - but we're not doing this so that it'll be easy.

So originally, I started trimming a little here and there to see how much of the original had to go...then I just got the plasma out and cut it all out. After the rest was fabricated (subframe) then I was thinking that there is NO way that I'll be happy with the spring rates or the valving of the shocks...or at least it's very unlikely, and changing the coil overs was starting to look like actual work. I avoid work - when I first met Evolvo67 at the IPD meet in 2009, he commented that I was "actively lazy" which is a very accurate description. I will work my fingers to the bone so that I don't have to do things twice. So with this as my defacto mindset, I knew that dropping the subframe to get at the top bolt on the shock tower was going to get old from below, and dropping the subframe in my little garage would suck.

So I got thinking that at the very least some form of access panel would be required. Then with the strut bar joining the towers, I didn't want to decrease the size of the trunk as one of the bonuses of the IRS is that you can have a flatish trunk floor. So that, with a little tape and cardboard became the BBQ lid. In the end, when it's out, I can service both coil overs (including removing them from the suspension uprights) with relative ease. It's actually a good usable space being 19" wide and 10" deep and around 12" tall. Good for a stuff sack or holding my helmet for racing or something.

Perhaps a nativity scene at Christmas...or a TV like "Pimp my ride". Na, wont do any of that.

I really didn't take a lot of pictures this weekend. Mostly doing a thousand details to finalize the sheet metal. Turning flanges, getting the fits perfect...it's all rather tedious and eats up a lot of time and doesn't look like anything has happened. Here are the highlights.

The bottom panel of the BBQ lid need to be welded in place to stop things floating around and causing havoc with the fit-up. So I turned a sheet metal return for the edge and hammered it over and then plug welded it to the lid. Then I added a little finishing angle so when it's screwed down it all comes up seamless. I really have to build a wheel instead of a crank for the bead roller...not the straightest effort on the beads. The ends were finished with a tool I made out of cheap leather punches from Princess Auto.

Then I fixed the attaching points for the sides where they contact the trunk panel. It needed flanges and some material added as I cut twice and it was still too short. No pictures of that. It worked.

Next, we have to attache the BBQ lid to the upper sheet metal closing panel. So clamp it up and get some holes drilled.

These were a PITA as my drill couldn't reach the flange straight so I had to use a long reach die grinder with a 1/8" bit. I needed the holes really straight to do the trick I wanted to do.

I'm using metric screws everywhere to be consistent. So I added metric M4 rivnuts (I used steel in this position as they are unlikely to see water) to pull the panel up perfectly.

The view from inside the BBQ lid - Stainless button heads are nice.

Here you can see the fasteners through the flange. I won't be closing this area in - if the screws don't come straight out, they'll just fall to the ground instead of rattling around inside a panel. So the only holes are clearance 8 mm access holes that will get finishing plugs on final assembly. These same screws will adorn the sides and bottom to attach this assembly.

I got a little side-tracked - I'm just finishing up the last of the details on the IRS install, and I noticed that I hadn't shared the part where I fabricated the ant-roll bar. For shame. I'm using a splined 3 piece NASCAR style bar as the ability to tune on a custom frame is important. Who knows how much sway bar I'm going to need? I'd like options that come in at around $80 shipped...in fine diameter increments. The standard brackets look like this and are Teflon bushed.

I whipped up a couple of brackets and thought I'd just drill them out to tap drill size, weld them on and tap the hole.

That went something like this.

Make mount.

Check hole centres.

Create overly complicated jig to get things in the proper alignment for tacking.

Smooth as silk. Only wasted 1/2 a day on this. Welding it took a few minutes.

I just need to finalize the sway bar links and this thing can go back up under the car. So first, a little wooden template.

A little bit of plastic tube that fit the hub perfectly.

Tried out some more wooden templates.

Ready to commit some designs to steel. 10 ga should do for the web of my little I-beam.

Yup, those look like they'll work. Used the scary giant belt grinder to finish these off - always worried about that thing finishing me off!

Grabbed my two steel arms.

Did a little cutting.

And a little bending.

Then welded it all back up. I did the cap with stringers - it just feels better than the weave and is better as it puts less head into the part.

Some grinding and we're done this part.

So that takes care of the out turn for the arms. They hit the mark right where I wanted them.

You can see here how the inside will place the link on the new tube and not on the weld or the old tube.

Now I just have to cut the arms and make the I-Beam section.

Time to finish these arms. First I cut off the majority of the arm and just kept the bent section. The rest won't be needed. So we start with welding the web blanks to these parts. They are keyed - so you have to be very careful how all this mounts together.

Carefully shimmed to get the web perfectly centred.

Then with one done, then I matched them up perfectly and welded the second arm to match the first.

I then cut the web blanks to the final shape and added the bar attachment ends, welded them on and ground it all flush.

Then I added the flanges.

This angle makes them look bent - they're just sitting on the welds and are splayed out. They're fine.
They've been finish welded and fit fine. I do have to build some adapters for the rear brakes, but that will wait for another update. I'm waiting on BOLTS of all things. So we'll show that when it's all done. It's another sad tale of "This part will work...I think. Mutter, mutter, mutter - frick - just engineer around a new damn part that is correct. (sound of S60R rear brake calipers hitting the scrap parts bin.)"

Great work as usual! I assume these are adjustable by just replacing the center part of the anti-roll bar with a thinner/thicker one?

Yes - they're the standard bar for NASCAR and other racing series and come in many, many different sizes. I'll run the same style on the front but will have to have custom bars cut as the track is pretty narrow.

If it helps validate the effort, I was scrolling through this thread until I got to that shot with all the clecos and the corrugated parcel shelf, and at that point, I stared in disbelief for a solid minute. I love details like this.

If it helps validate the effort, I was scrolling through this thread until I got to that shot with all the clecos and the corrugated parcel shelf, and at that point, I stared in disbelief for a solid minute. I love details like this.

Here's what I'm worried about right now. This inner fender is just not very strong. Even in stock form they are prone to cracking and need to be reinforced. Volvo did some bush-repair on the later 123 GT's which made it onto other 122's later on...but it's only a bandage. I don't like this solution.

I was going to tie the new suspension into this flawed part but it wasn't sitting very well. So out came the cardboard and tape again.

Played around with this as an idea for a while...decided it was just bandages again and therefore suboptimal. So I ditched that - and broke out the drinking straws.

That lead to larger ABS "straws" LOL. And a little orange tape.

And a quick trip to the border in a snow storm to get 1.75 X 0.095" DOM tube (they wanted $14 a foot in Canada for this stuff!).

I then quit playing around with the frame and built a frame table and jig for the frame.

Simulated rear cross member detail shot. I need more clamps.

I'm going to roll out a YouTube Channel for this build.

Front end goes in next week (when I get around to tacking it up and test fitting and trying it out again...and convincing myself that drinking straws are a workable solution (I'm familiar with Herb Adams's Chassis Engineering book). Then I'll toss that tube in my newly built tube bender and get this thing rolling. My goal was to have it as a roller by the fall. Now in Canada, that has a different meaning. We've already had a foot of snow, but fall doesn't end until December. So I've got time.